I agree with BVR, why would you have LED's in dark areas unless you are in the business of making drivers and LED's. I don't believe ours do (Australia). A properly designed driver would consume only nanoamps when off though.
The snow comment made by MD17 suggests an integral heater that only runs when frosty might offer the best of both worlds.
Low Energy Traffic Signals are not always a good thing; Here in the snowy North you can always identify LED based traffic signals-- they are the snow encrusted objects hanging from poles at busy intersections. Depending on the air temperature and rate of snow fall, you may or may not be able to see a dim glow emanating from the clump of snow.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.